Process for detarnishing and inhibiting copper and copper alloys



United States Patent "ice soluble in water.

3,274,114 PROCESS FOR DETARNISHING AND INHIBITING COPPER AND COPPER ALLOYS Tibor Thomas Grof, 6517 Landover Road, 203, Cheverly, Md. No Drawing. Filed Nov. 4, 1965, Ser. No. 506,407 3 Claims. (Cl. 252-100) The present application is a continuation-in-part of my prior application Serial No. 323,231, filed November 13, 1963, and now abandoned, which in turn is a continuation-impart of my earlier application Serial No. 189,645 filed April 23, 1962, and now abandoned.

This invention generally relates to a composition that has both tarnish removing and tarnish inhibiting properties and which is particularly useful in connection with copper or copper-containing alloys.

Copper and copper-containing alloys, such as brass, bronze, and similar compositions, get a dark tarnish when exposed to air. This tarnish is partly caused by oxygen and/or carbon dioxide and traces of hydrogen sulfide and is difficult to remove.

In most cases, in order to remove such a tarnish, an abrasive has to be used in liquid, paste, or wax form.

A really successful combined tarnish remover and tarnish inhibitor for copper and copper-containing alloys has not been available on the market prior to this invention, although there is an urgent need for this type of composition. A great many items used in everyday life are made from copper and copper-containing alloys (such as doorknobs, radiators, electrical fixtures, etc.) and there is an ever-increasing use of these materials in ornamental pieces, statues and in the electronic and instrumentation industries. All of these items get tarnished within a rather short time. This tarnish is relatively hard to remove by hand, even when using abrasive-containing cleaning products. Removal of tarnish from delicate printed circuits is often an impossible task to perform by hand.

The use of acid, such as nitric acid, removes not only the tarnish but attacks the copper as well. Cleaning by rubbing with cyanides is successful but has a very limited usage because of its highly poisonous character.

The present invention provides a way to detarnish copper and copper-containing alloys by simple dipping, brushing or spraying. The tarnish is removed in an extremely short time and the detarnisher is easily flushed from the surface with water, or removed in any other suitable manner. The copper or copper-containing alloy remains clean and does not easily retarnish after this treatment. In fact, the treatment with the composition of the present invention inhibits retarnishing for a period that has been previously achieved only by using a protective coating.

Considered from one aspect, my novel metal detarnishing and tarnish inhibiting composition consists essentially of: 7x

(a) 540% by weight of sulfamic acid;

(b) 540% by weight of a compound selected from the group consisting of (1) hexavalent chromium salts (such as sgdiumbicblqlnalo, ammonium bichromate and potassium bichromate) and (2) anhydrides of hexavalent chromium compounds (such as chromic acid), and

(c) Enough water to bring the total weight percentage up to 100%.

By hexavalent chromium salts, what is meant is the alkali, alkaline-earth and the ammonium salts of the chromium ions -Cr O and --CrO Chromic acid, CrO may also be used. For use in an aqueous solution, of course, these chromium compounds must be Generally, the single valence alkali, alkaline-earth and ammonium salts of the hexavalent 3,274,114 Patented Sept. 20, 1966 chromium ions CI'2O7 and C10,, all being water soluble or water soluble in the presence of mineral acids, are those which will be used in the present invention. The ammonium, sodium and potassium salts are preferred.

When the chromates of ammonium, sodium and potassium are used in acid solution, these will be converted to the corresponding bichromates.

A preferred metal detarnishing and tarnish inhibiting composition in accordance with this invention comprises:

(a) 1020% by weight of sulfamic acid,

(b) 10-20% by weight of a compound selected from the group consisting of hexavalent chromium salts and chromic acid, and

(c) Enough water to bring the total weight percentage up to 100%.

The pH of the composition in accordance with this invention preferably ranges between about 0.1 and 5.0 and most preferably between about 1 and 3.

The following examples illustrate some preferred compositions in accordance with this invention. The parts are by weight.

Example 1 A. 15 parts of sulfamic acid 10 parts Of Kgcl'goq parts of water 15 parts of sulfamic acid 10 parts of Na Cr O 75 parts of water 15 parts of sulfamic acid 10 parts Of (NH4)2CI'2O7 75 parts of water Example 2 10 parts of sulfamic acid 15 parts of K Cr O 75 parts of water Example 3 20 parts of sulfamic acid 10 parts of K Cr O, 70 parts of water Sulfamic acid alone or the hexavalent chromium compounds alone will not give a satisfactory detarnishing action. It is the combination of these two components which gives outstanding results. There is apparently some synergistic effect besides the action of an acid reaction which occurs when this combination is employed, since the additive effect of each component alone does not equal the effect achieved with the combination. Also, combinations of sulfuric acid and hexavalent chromium compounds do not achieve the same result as the present invention.

OTHER INGREDIENTS There are a number of other materials that may be added to the above recited components to improve the utility of the composition for certain specified purposes. These materials are preferably added in small amounts in place of part of the water. These materials are not new per se and in fact have probably been used in other detarnishing compositions. Such materials include 1-10% by weight of a wetting agent or surfactant (such as alkyl aryl sulfonates, lauryl alcohol derivatives, highly sulfonated fatty acid esters, ethylene oxides and alkyl phenol condensates, etc.). Another suitable additive would be a minor amout (1-20% by weight) of a solvent-type ingredient, preferably Water soluble, oil dissolving organic solvents (such as dioxane, diacetone-alcohol, etc.). The wetting agent, surfactant, and solvent primarily function to penetrate and remove any hydrophobic layer (such as oil or grease) which is on the metal to thereby give ingredients (a) and (b) above a chance to perform their detarnishing and tarnish inhibiting action.

A small amount (e.g. less than 5%) of a free mineral acid, such as sulfuric, hydrochloric or phosphoric, may also be added if desired, the mineral acid apparently functioning to accelerate and catalyze the action of the other ingredients.

A small amount (-5%) of a copper complex forming acid, such as tartaric acid or citric acid may also be added.

A small amount (1-5%) of a known tarnish inhibitor such as the mercaptans or the various thioureas may also be added.

These additional ingredients are not essential and should not generally exceed greater than 45% of the composition. It is preferred that such added ingredients correspond to no more than about 10-15% of the com position.

Examples of additional preferred compositions in accordance with this invention are listed below, the parts being by weight.

Example 4 10 parts of sulfamic acid 15 parts of Na Cr O 6 parts of dioxane 2.0 parts of sulfuric acid 67 parts water Example 5 15 parts of sulfamic acid 15 parts of K Cl207 5 parts of dioxane 2.5 parts of sulfuric acid 62.5 parts of water Example 6 The composition of Example 5 is used except that the potassium bichromate is replaced by potassium chromate. In acid solution the chromate is converted to bichromate. .The same results occur with the ammonium and sodium chromates.

The novel compositions of this invention are (gener .ally) used in liquid form, preferably aqueous solutions.

However, those skilled in the art will realize that embodying the components in pastes or waxes is conceivable for certain purposes.

The safety of the composition of this invention is an extremely important feature. There is no danger that there will be spontaneous burning of clothes or other organic material, especially if the liquid dries on these materials.

More or less detailed claims will be presented hereinafter and even though such claims are rather specific in nature, those skilled in the art to which this invention pertains will recognize that there are obvious equivalents for the specific materials recited therein. Some of these obvious equivalents are disclosed herein. Other obvious equivalents will immediately occur to one skilled in the art and still other obvious equivalents could be readily ascertained upon rather simple, routine, non-inventive experimentation. I intend that all such obvious equivalents be encompassed within the scope of this invention and patent grant, as well as changed proportions of the ingredients which do not render the composition unsuitable for the disclosed purposes.

What is claimed is:

1. A method of detarnishing and inhibiting further tarnishing of a material selected from the group consisting of copper and copper alloys which comprises treating said material with a composition consisting essentially of (a) 5-40% by weight of sulfamic acid (b) 540% by weight of a compound selected from the group consisting of (1) water soluble hexavalent chromium salts of the anions -Cr O and -CrO and the cations sodium, potassium and ammonium and (2) chromic acid, and (c) water to bring the total weight percentage up to percent.

2. A method in accordance with claim 1 wherein said mixture comprises about 15% by weight of sulfamic acid, about 15% by weight potassium bichromate, about 5% of dioxane, about 2 /z% sulfuric acid and about 62 water.

3. A method in accordance with claim 1 wherein said mixture further includes minor amounts of materials selected from the group consisting of wetting agents, water-soluble oil-dissolving organic solvents, free mineral acids, copper complex forming acids, and mixtures thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,428,804 10/ 1947 Terry et al. 252-100 2,837,484 6/1958 Sway et a]. 252100 2,902,390 9/1959 Bell. 2,941,949 6/1960 Saukaitus 252-151 LEON D. ROSDOL, Primary Examiner.

ALBERT T. MEYERS, Examiner.

M. WEINBLATI, Assistant Examiner. 

1. A METHOD OF DETARNISHING AND INHIBITING FURTHER TARNISHING OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF COPPER AND COPPER ALLOYS WHICH COMPRISES TREATING SAID MATERIAL WITH A COMPOSITION CONSISTING ESSENTIALLY OF (A) 5-40% BY WEIGHT OF SULFAMIC ACID (B) 5-40% BY WEIGHT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF (1) WATER SOLUBLE HEXAVALENT CHROMIUM SALTS OF THE ANIONS -CR2O7 AND -CRO4 AND THE CATIONS SODIUM, POTASSIUM AND AMMONIUM AND (2) CHROMIC ACID, AND (C) WATER TO BRING THE TOTAL WEIGHT PERCENTAGE UP TO 100 PERCENT. 